CCNT cheat sheet

Upper motor neuron lesions produce spasticity, hyperreflexia, and Babinski sign; lower motor neuron lesions produce flaccidity, atrophy, fasciculations, and areflexia.

The pyramidal (corticospinal) tract decussates in the medulla; the lateral corticospinal tract controls distal limb muscles.

The basal ganglia modulate movement via direct (facilitatory) and indirect (inhibitory) pathways; dopamine from substantia nigra pars compacta facilitates the direct pathway.

The cerebellum coordinates voluntary movement, balance, and motor learning; lesions cause ipsilateral ataxia, dysmetria, and intention tremor.

The thalamus is the major sensory relay to the cortex (except olfaction); the VPL relays body sensation, VPM relays face sensation.

The brachial plexus derives from C5–T1 roots; the lumbosacral plexus from L1–S4; nerve root compression produces radicular pain in a dermatomal pattern.

The autonomic nervous system: sympathetic preganglionic fibers are thoracolumbar (T1–L2), parasympathetic are craniosacral (CN III, VII, IX, X, S2–S4).

The circle of Willis connects anterior and posterior circulations via the anterior and posterior communicating arteries; the middle cerebral artery supplies the lateral cortex and internal capsule.

The blood-brain barrier is formed by tight junctions of capillary endothelial cells, astrocytes, and pericytes; it excludes many drugs and large molecules.

Differential amplifier rejects common-mode signals; common-mode rejection ratio (CMRR) = 20 log10(differential gain / common-mode gain), ideally >100 dB.

Input impedance of an EEG amplifier should be at least 10 MΩ (ideally >100 MΩ) to minimize signal attenuation from high electrode impedance.

The Nyquist theorem: sampling rate must be at least twice the highest frequency of interest; for EEG up to 70 Hz, sample at ≥140 Hz (commonly 256–512 Hz).

Analog-to-digital resolution: 1 LSB = full-scale voltage / 2^n; a 16-bit ADC over ±5 V has LSB ≈ 0.15 µV.

High-pass filter (low-frequency filter) removes slow drift; low-pass filter (high-frequency filter) removes muscle and mains noise; notch filter removes 50/60 Hz.

Patient leakage current limits: <100 µA normal condition, <500 µA single-fault condition for type BF/CF applied parts (IEC 60601-1).

Ground electrode is not a current return path for the patient; it provides a reference for the amplifier and must be connected to earth.

Impedance should be balanced across active and reference electrodes; imbalance degrades CMRR and increases 60 Hz artifact.

International 10–20 system: electrodes placed at 10% or 20% of the nasion–inion and preauricular distances; odd numbers left, even numbers right, z midline.

Referential montage uses a common reference (e.g., Cz, linked ears, average); bipolar montage displays differences between adjacent electrodes in chains.

The longitudinal bipolar (double banana) montage chains: Fp1-F3-C3-P3-O1 and Fp2-F4-C4-P4-O2, plus temporal chains Fp1-F7-T3-T5-O1 and Fp2-F8-T4-T6-O2.

The transverse bipolar montage chains across the head: F7-F3-Fz-F4-F8, T3-C3-Cz-C4-T4, T5-P3-Pz-P4-T6.

Polarity convention: input 1 more negative than input 2 produces an upward deflection (negative up).

Electrode impedance should be <5 kΩ and balanced; check impedance before and periodically during recording.

The 10–20 system includes Fp1/2, F3/4, C3/4, P3/4, O1/2, F7/8, T3/4, T5/6, Fz, Cz, Pz; additional electrodes (e.g., T1/T2, Oz) may be used.

Activation procedures: hyperventilation (3–5 min) provokes absence seizures and slowing; photic stimulation at 1–30 Hz assesses photoparoxysmal response.

Normal adult awake background: posterior alpha rhythm 8–13 Hz, reactive to eye opening; beta activity >13 Hz often frontal.

Normal sleep stages: N1 (theta, vertex sharp waves), N2 (sleep spindles 12–14 Hz, K-complexes), N3 (delta <2 Hz, >75 µV), REM (low-voltage mixed frequency, sawtooth waves).

Benign variants: mu rhythm (7–11 Hz, arch-shaped, central, reactive to movement), 14 and 6 Hz positive bursts, wicket spikes, rhythmic midtemporal theta of drowsiness (RMTD).

Epileptiform discharges: spikes (<70 ms), sharp waves (70–200 ms), spike-and-wave complexes; 3 Hz generalized spike-wave is classic for absence epilepsy.

Focal slowing (delta/theta) suggests a structural lesion; generalized slowing suggests encephalopathy or metabolic disturbance.

Periodic patterns: PLEDs (periodic lateralized epileptiform discharges) in acute structural lesions; triphasic waves in metabolic encephalopathy (often hepatic).

Burst suppression: high-voltage bursts alternating with suppression, seen in deep anesthesia, hypothermia, or severe encephalopathy.

Electrocerebral inactivity (ECI): no activity >2 µV during a 30-minute recording at increased sensitivity; used in brain death determination.

Visual evoked potential (VEP): pattern-reversal stimulation; P100 wave (positive, ~100 ms) is the most reliable; prolonged latency in optic neuritis and demyelinating disease.

Brainstem auditory evoked potential (BAEP): waves I–V; wave I from auditory nerve, wave III from superior olive, wave V from inferior colliculus; interpeak I–III, III–V, I–V latencies.

BAEP is resistant to sedation and useful in comatose patients; prolonged I–V interpeak latency suggests brainstem dysfunction.

Somatosensory evoked potential (SSEP): median nerve stimulation at wrist, recording over Erb's point, cervical spine (N13), and scalp (N20); prolonged N20 latency indicates central conduction delay.

SSEP of posterior tibial nerve records lumbar (N22), cervical, and cortical (P37) responses; useful for spinal cord monitoring.

For SSEP, limb temperature should be kept warm (>32°C) because hypothermia prolongs latencies.

Evoked potential waveforms are averaged over hundreds to thousands of trials to improve signal-to-noise ratio; artifact rejection is essential.

In intraoperative monitoring, SSEP and MEP changes >50% amplitude or >10% latency increase warrant alerting the surgeon.

Motor nerve conduction: supramaximal stimulation, record compound muscle action potential (CMAP); measure latency, amplitude, conduction velocity, and F-wave.

Sensory nerve conduction: record sensory nerve action potential (SNAP); amplitude reflects axonal loss, latency reflects demyelination.

Conduction velocity (m/s) = distance (mm) / latency difference (ms); typical median motor velocity 49–65 m/s.

Prolonged distal latency and slowed conduction velocity with preserved amplitude suggest demyelination; reduced amplitude with normal velocity suggests axonal loss.

F-wave latency reflects proximal conduction; prolonged F-wave suggests radiculopathy or proximal demyelination.

EMG: insertional activity, spontaneous activity (fibrillations, positive sharp waves), motor unit action potentials (MUAPs), and recruitment pattern.

Fibrillations and positive sharp waves indicate active denervation; large polyphasic MUAPs indicate chronic reinnervation.

Reduced recruitment (fewer MUAPs firing faster) suggests neuropathic loss; early recruitment of small MUAPs suggests myopathy.

H-reflex assesses S1 root and tibial nerve; prolonged H-reflex latency suggests S1 radiculopathy.

Hand hygiene is the single most effective infection control measure; use alcohol-based rub or soap and water before and after patient contact.

Standard precautions apply to all patients: gloves for contact with blood/body fluids, gowns for splashes, masks/eye protection as needed.

Needlestick injury: wash with soap and water, report immediately, and follow post-exposure prophylaxis protocol; HIV PEP should start within hours.

Electrode application sites should be cleaned with alcohol and dried; abraded skin increases infection risk and should be avoided unless necessary.

Patients with implanted cardiac pacemakers or defibrillators require careful electrode placement and monitoring; avoid current paths through the chest.

Seizure during EEG: note time, duration, and semiology; do not restrain the patient; protect from injury; suction and oxygen available.

Fall precautions: assist patients with mobility issues; ensure bed rails and call bell within reach.

Documentation of patient care includes vital signs, medications, allergies, and any adverse events during the procedure.

Informed consent must be obtained before invasive or non-routine procedures; document the discussion and patient understanding.

Patient confidentiality is protected by HIPAA; disclose information only on a need-to-know basis and secure records.

Scope of practice: technologists perform tests and report findings but do not independently diagnose or prescribe treatment.

Documentation must be accurate, timely, and legible; include date, time, procedure, patient response, and any deviations from protocol.

Avoid altering records; corrections should be dated, signed, and explained, with the original entry still visible.

Report unsafe practices or equipment malfunctions through the chain of command and incident reporting systems.

Professional boundaries: do not accept gifts that could influence judgment; avoid dual relationships with patients.

Continuing education and certification maintenance (e.g., ABRET) are required to ensure competence and uphold professional standards.